Processes for separating an isobutane recycle stream from a mixed C4 stream

Abstract

Processes for providing an isobutane recycle stream to be recycled to a dehydrogenation zone. In some embodiments a dividing wall column is used to separate a hydrogenation effluent. The hydrogenation effluent may include olefins, or it may be fully saturated. A hydrogenation zone may include a nickel based catalyst and may fully saturate dienes and olefins, or only hydrogenate dienes.

What is claimed is: 
     
       1. A process for converting hydrocarbons, the process comprising:
 dehydrogenating isobutane to provide an isobutene rich stream in a dehydrogenation zone; 
 reacting isobutene with methanol to provide an effluent stream, the effluent stream comprising methyl tert-butyl ether; 
 separating a methyl tert-butyl ether product stream from a C4 stream, the C4 stream comprising 1-butene and 2-butene; 
 hydrogenating at least a portion of the C4 stream in a hydrogenation zone to provide a hydrogenated effluent, wherein the hydrogenation zone is operated to fully hydrogenate all olefins and dienes; 
 separating the hydrogenated effluent, using a rerun column, into an isobutane recycle stream, a normal paraffin stream comprising normal butane, and a propane stream; and, 
 recycling the isobutane recycle stream to the dehydrogenation zone. 
 
     
     
       2. The process of  claim 1  further comprising:
 removing oxygenates from the C4 stream before hydrogenating at least a portion of the C4 stream in the hydrogenation zone. 
 
     
     
       3. The process of  claim 1  wherein the hydrogenation zone includes a nickel based catalyst. 
     
     
       4. The process of  claim 3  further comprising:
 injecting sulfur into the hydrogenation zone to selectively hydrogenate dienes in the C4 stream. 
 
     
     
       5. The process of  claim 4  further comprising:
 selectively isomerizing 1-butene to 2-butene in the hydrogenation zone. 
 
     
     
       6. The process of  claim 5  wherein a conversion ratio of 2-butene to 1-butene is at least 8:1. 
     
     
       7. The process of  claim 5  wherein a conversion ratio of 2-butene to 1-butene is at least 12:1.